interface Com {
   int add(int a,int b);
}
abstract class A {
   abstract int add(int a,int b);
}
class B extends A implements Com{
   public int add(int a,int b) {
     return a+b;
   }
}
public class F {
public static void main(String args[]) {
   B b = new B();
   Com com = b;
   System.out.println(com.add(12,6));  //代码1
   A a = b;
   System.out.println(a.add(10,5));    //代码2
  }
}
